The prior filter devices include, among others, so-called spin-on filters. In their filter housing parts, a filter element designed especially for the respective filtration task is integrated. If the filter element is clogged with dirt causing the filter device to become unusable for its filtration task, the entire filter device, that is, the filter housing in addition to the filter element, must be replaced by a new filter device. This replacement has the disadvantage that the entire unit must be disposed of, although the actual filter housing part would still be usable. To remedy this situation, conventionally in the spin-on filter only the used filter element need be replaced such that the filter housing part with a new filter element can be used as a newly assembled filter device, especially for removing dirt from hydraulic circuits. Fundamentally, the problem arises that operators or even specially trained maintenance personnel forget to use a new filter element. Then, the reconnected filter housing part designed as a screw-in cartridge, even without the filter element, enables operation of the hydraulic system, but without dirt in the fluid flow being removed. Serious damage to the entire hydraulic system can then occur. Comparable problems also arise for other fluid media such as gases or pasty media.
To be able to establish greater operating reliability in this respect, DE 10 2004 014 149 A1 discloses a quarter-turn fastener as a fastening means by which the filter housing can be detachably mounted on the fluid means of the hydraulic circuit. By the rotary motion of the filter housing when the quarter-turn fastener is released and locked, a blocking part is controllable which blocks and clears the pertinent fluid connection. In this way, the filter can be reliably changed. A comparably designed solution is also shown in DE 10 2004 008 879 A1, where, instead of the quarter-turn fastener, a stopper with a plate-shaped slide part is provided for blocking and clearing the fluid connections. These solutions are very reliable in operation. Both the quarter-turn fastener and the stopper however require a relatively large amount of installation space, and thus, engender the corresponding production costs.